Geophysical surveying (e.g., seismic, electromagnetic) is a technique where two-or three-dimensional “pictures” of the state of an underground formation are taken. Geophysical surveying takes place not only on land, but also in marine environments (e.g., ocean, large lakes). Marine geophysical survey systems use a plurality of sensor cables, which contain one or more sensors to detect acoustic energy emitted by one or more sources and returned from a hydrocarbon reservoir and/or associated subsurface formations beneath the sea floor. Sensor cables, in some embodiments may comprise sensor streamers which may be towed through a water body by a survey vessel, and in other embodiments ocean bottom cables disposed on the sea floor or entrenched within the seabed. Detection and interpretation of the signals represented thereby can be complicated by reflections of the energy from interfaces present in the marine environment, particularly the water-air interface at the surface of the sea or similar water body. Similarly, the detection and interpretation of such signals may be complicated by acoustic noise emitted by sources in the marine environment.
Discrimination against reflected signals or noise sources may be provided by combining signals from multiple detector types sensitive to different physical characteristics of the acoustic signal. For example, when appropriately combined, the output from hydrophones sensitive to the pressure perturbation from the acoustic signal may be used in conjunction with the output of a particle motion sensor sensitive to the velocity of a particle for example, a geophone, may provide such discrimination. Further, when appropriately combined with the output of a three-component particle motion sensor, discrimination against reflected signals and/or noise sources may be provided based on the directional properties of the signals or noise sources.